ROLLER SCREEN WITH ECCENTRIC DISCS

Abstract: A roller screen comprises a trough whose bottom is formed of a plurality of parallel shafts (4), each having a plurality of circular discs (10) which are separated by spacer rollers (11). The discs on each shaft are so arranged as to alternate with the discs on the adjoining shaft or shafts and project into grooves (15) provided in the spacer rollers of the adjoining shaft or shafts. Furthermore, the discs are eccentrically mounted on the respective shafts, the discs on each shaft having an eccentricity that is circumferentially offset from disc to disc. The spacer rollers are made of rubber and are concentric with respective shafts. The grooves of the spacer rollers allow axial as well as radial clearance for the discs.

Description: ROLLER SCREEN WITH ECCENTRIC DISCS. This invention relates to a roller screen comprising a trough whose bottom is formed of a plurality of paral¬ lel shafts, each having a plurality of circular discs which are separated by spacer rollers, the discs on each shaft being so arranged as to alternate with the discs on the adjoining shaft or shafts. Roller screens of this type are previously known and are, among other things, used for screening various soil conditioners, such as peat. In screening, all the shafts are rotated in the same direction, and the material put in the trough is then moved along the bottom thereof by the rollers and the discs and is screened through the gaps between adjoining shafts. Thus, the discs not only contribute to convey the material along the bottom of the trough, but also make the screen self-cleansing. The object of the present invention is to further enhance the efficiency of such prior-art roller screens, while retaining their compact design and vibrationless operation. According to the invention, this object is attained by a roller screen of the above type, which is character¬ ised in that the discs are eccentrically mounted on the respective shafts, the eccentricity being circumferen- tially offset from disc to disc on each shaft, and pro- ject into grooves provided in the spacer rollers of the adjoining shaft or shafts, that the spacer rollers are made of rubber and are concentric with the respective shafts, and that the grooves of the spacer rollers allow axial as well as radial clearance for the discs . In this way, an upward as well as forward movement will be imparted to the screening material, resulting in more efficient conveyance along the bottom of the trough, SUBSTITUTESHEET as well as in more efficient screening due to the agita¬ tion of the screening material during its conveyance. The agitation of the screening material thus con¬ veyed is further promoted by the special eccentric arrangement, yielding even more efficient screening. The eccentricity of the discs is taken up in a manner that enhances screening efficiency owing to the fact that the discs project into grooves provided in the spacer rollers of the adjoining shaft or shafts and that the spacer rollers are concentric with the respective shafts. Combined with the axial and radial clearance, such design of the spacer rollers contributes to effi¬ cient cleansing. In a preferred embodiment, the shafts are square shafts and the discs have matching square holes, such that the offset of the eccentricity may amount to 90° from one disc to the next. In tests, it has been found that the Shore hardness of the spacer rollers preferably amounts to 70-80. With such hardness, which is comparatively critical, the fric¬ tion between the rollers and the screening material is high, resulting in rapid screening. One embodiment of a roller screen according to the invention will be described in more detail below with reference to the accompanying drawings, in which Fig. 1 is a perspective view of a roller screen ac¬ cording to the invention; Fig. 2 is a view illustrating the construction of one of the shafts, with associated discs and spacers, that forms part of the roller screen in Fig. 1; and Fig. 3 is a top plan view of one of the discs in Fig. 2. As illustrated in Fig. 1, a roller screen comprises a frame 1 having two longitudinal beams 2, 3, in which a plurality of parallel shafts 4 are mounted. The frame 1 further supports a trough having side walls 5, 6 and an end wall 7. The shafts 4 form the bottom of the trough. In operation, the shafts 4 are rotated in the same direction by means of a chain (not shown) driven by a motor 8 and engaging gear wheels 9 (Fig. 2), one such gear wheel being arranged at one end of each shaft . In Fig. 1, the screening material introduced at the end wall 7 is conveyed towards the farther open end of the trough while being screened between the shafts 4. As shown in Fig. 2, each shaft 4 is provided with a plurality of circular discs 10 which are separated by spacer rollers 11 made up of two identical parts 12, 13. Each part 12, 13 comprises a portion 14 of reduced diame¬ ter, and the parts 12, 13 are reversedly arranged between the discs 10 to form a central groove 15 between each pair of discs 10. An abutment disc 16 is fixed on the shaft 4, e.g. by welding, at a distance from one end thereof. The discs 10 and the rollers 11 are located between the abutment disc 16 and a stop disc 17 provided at the other end of the shaft 4 and movable along the shaft. Further, the shaft 4 is mounted in the beams 2, 3 by means of ball bearings 18, 19. Outwardly of the stop disc 17, the shaft 4 is threaded and carries a nut 20 for clamping the discs 10 and the spacer rollers 11 together. A spacer bushing 21 is arranged between the part of the ball bearing 18 that is fixed in relation to th shaft 4 and the nut 20. The gear wheel 9 is provided outwardly of the ball bearing 18. Outwardly of the gear wheel 9, the shaft 4 is threaded in order to receive a lock nut 22. Finally, the position of the shaft 4 in relation to the beams 2, 3 is fixed by means of a nut 24 provided out- wardly of the ball bearing 19. The shaft 4 is square at least along that part which carries the discs 10 and the spacer rollers 11. The discs 10 are provided with matching, eccentric square holes 23 (Fig. 3) . The spacer rollers 11 are also provided with square holes, but these are concentrically arranged. As indicated in Fig. 2, the shafts 4 are located at such a distance from one another that the discs of one shaft 4 project into the grooves 15 of the adjoining shaft or shafts, while allowing a certain clearance with respect to the side walls as well as the bottom of the groove 15. As a result of the eccentric arrangement of the discs 10 on the shaft 4, the clearance with respect to the bottom of the groove 15 will vary. According to the invention, this clearance preferably is at least 5 mm, while the clearance in the groove 15 on both sides of each disc 10 conveniently is about 2 mm. Such an arrangement results in maximum cleansing effect. According to the invention, the eccentricity of the discs 10 should be offset from one disc to the next. In the embodiment illustrated in Fig. 2, this is achieved, • starting from discs 10 of exactly the same rotational position, by rotating each disc 10 through 90° in rela¬ tion to the preceding disc when passing it onto the shaft 4. The eccentricity will then be offset by 90°, which will improve conveyance as well as screening efficiency. In addition, the shaft 4 is maintained in balanced state, enabling vibrationless operation of the roller screen. According to the invention, it is further a desid¬ eratum that the spacer rollers 11 are made of a material of suitable hardness. Tests have shown that the Shore hardness should amount to 70-80. The spacer rollers 11 are conveniently made of rubber, which provides good frictional contact with the screening material at the indicated hardness. With spacer rollers 11 of suitable axial extent, such hardness further enables the discs 10 to be fitted into the grooves 15 by pressing together, by means of the nut 20, the assembly made up of the discs 10 and the spacer rollers 11. In actual practice, the discs 10 may have a diameter of 85-150 mm and a width of 3 mm and be made of steel. The spacer rollers 11 may have a maximum diameter of 75 mm, and the groove 15 may have a depth of 15 mm and a width of 7 mm. The eccentricity of the discs 10 in rela¬ tion to the shaft 4 may amount to 2 mm. According to the invention, the axial offset of the discs 10 of one shaft 4 in relation to the discs 10 of the adjoining shaft or shafts 4 is easily obtained by dividing the spacer rollers 11 into two equal parts 12, 13. It goes without saying that the roller screen de¬ scribed above can be modified in many ways within the scope of the invention. For instance, the single discs 16, 17 can be replaced with double discs provided with an intermediary spacer sleeve, in which case parts of the trough walls 5, 6 may project into the gaps between the double discs in order to achieve lateral sealing of the trough.

Claims: CLAIMS 1. A roller screen comprising a trough (5-7) whose bottom is formed of a plurality of parallel shafts (4), each having a plurality of circular discs (10) which are separated by spacer rollers (11), the discs on each shaft being so arranged as to alternate with the discs on the adjoining shaft or shafts, c h a r a c t e r i s e d in that the discs (10) are eccentrically mounted on the re¬ spective shafts (4), the eccentricity being circumferen- tially offset from disc to disc on each shaft, and pro¬ ject into grooves (15) provided in the spacer rollers of the adjoining shaft or shafts, that the spacer rollers (11) are made of rubber and are concentric with the re¬ spective shafts (4), and that the grooves (15) of the spacer rollers (11) allow axial as well as radial clear¬ ance for the discs (10) . 2. A roller screen as set forth in claim 1, c h a r a c t e r i s e d in that the offset is 90°. 3. A roller screen as set forth in claim 1 or 2, c h a r a c t e r i s e d in that the spacer rollers (11) are made of rubber having a Shore hardness of about 70- 80. 4. A roller screen as set forth in any one of claims 1-3, c h a r a c t e r i s e d in that each spacer roller (11) is made up of two identical parts (12, 13) . 5. A roller screen as set forth in any one of claims 1-4, c h a r a c t e r i s e d in that the axial clear¬ ance on each side of the disc (10) is in the order of 2 mm. 6. A roller screen as set forth in any one of claims 1-5, c h a r a c t e r i s e d in that the radial clearance does not exceed about 5 mm.

Inventors: ANDERSSON NILS EINAR, ANDERSSON PER-AKE, ANDERSSON, NILS, EINAR, ANDERSSON, PER-AKE
Applicants: SPANAK I GOEINGE AB
Application year: 1994
Main classification: B07B1
IPC codes: B07B1